Sharpening is a common task for wood workers. Artisans the world over are constantly seeking apparatus and methods to produce a sharp edge on their tools, as only with a sharp tool can fine woodworking be achieved. For instance, a joint between two pieces of wood can only be effected if the wood is accurately formed, and such accuracy requires sharp tools. Chisels, plane blades, carving tools, axes, drawknifes, and other tools all must be prepared for use by grinding and polishing two intersecting surfaces to create a keen cutting edge or arris. However, used tools dull with use, so periodic sharpening is necessary. Many tool sharpening devices and techniques have been developed, but tool sharpening remains difficult for many tool users, primarily because sharpeners applied to the cutting edge of tools are not easily positioned accurately to produce the desired edge, and not consistently positioned so that the same angle and overall orientation is achieved from one re-sharpening to the next.
In some tools, this variation from one sharpening to the next is acceptable, or perhaps unavoidable. For instance, in pruners, the cutting edge of the pruner is generally short and curved, and the green wood through which the cutting edge will be drawn is soft. As a result, a few moments dressing a pruner may be sufficient to create a cutting edge of sufficient sharpness which will last an entire season. However, when working with dry and seasoned hardwoods, frequent sharpening of chisels and other cutters is necessary. Thus, cabinet makers and other wood workers often find their tools require dressing many times in a week. However, substantial practice, skill and time is required to utilize many sharpening devices and techniques, and wide-spread unfamiliarity with well-sharpened tools make it difficult for many tool users to accurately judge the quality of sharpening results. As a result, a simple apparatus and method to accurately position the edge of a Held Tool against a sharpener allows wood workers to create an edge of the proper shape. Such apparatus or method also orients a tool in relation to the sharpener to allow frequent sharpening without unnecessary loss of tool metal.
All relevant sharpening techniques involve abrading a Held Tool surface with abrasive materials, such as natural or man-made stones, or with abrasive particles deposited on another substrate. Among existing products intended for sharpening woodworking hand-tools are high-seed, “dry” grinding wheels that generally do not use lubrication, and low-speed “wet” wheels that use lubrication, typically water, on the wheel surface. Some of these products utilize relatively large diameter vertical wet or dry grinding or honing wheels, where the wheel edge is the principal working surface. Others utilize horizontal wheels where one face of the wheel is the principal working surface. A variety of abrasive “stones,” usually having flat surfaces, are also available for manual sharpening.
A major difficulty with use of all abrasive wheels and manual stones, however, is maintaining proper orientation of the Held Tool, the tool which must be sharpened, in relation to the wheel or stone, the tool intended to act against the Held Tool so as to remove metal from the Held Tool in a desired manner. As noted above, proper orientation, consistently applied with each sharpening, optimally dresses an edge without unnecessary loss of metal from the Held Tool, and with minimal time and effort from the artisan who must restore the desired shape and sharpness. The challenge is to establish an optimal geometry between the Held Tool and the stone, and consistently reproduce that optimal geometry with each re-sharpening. Only by maintaining that same (optimal) geometry with each re-sharpening can a wood worker reproduce the correct sharpening angle and distance, and thereby merely dress the edge of the Held Tool without removing excessive metal, while requiring minimal time. Only by maintaining geometry with each re-sharpening can a wood worker insure a proper shape, that is, the shape which is optimal for cutting the desired shape for the task at hand.
Apparatus and methods for sharpening the edge of a tool are common, and various guides have been employed in an attempt to achieve easier and more accurate sharpening. Such guides may be as simple as a simple bar, suspended in a fixed or semi-fixed position over the grinding wheel or disk, against which the user may rest the Held Tool as it is lowered on to the moving wheel or disk. However, in the effort to create guides which more accurately hold the Held Tool, such guides are often more elaborate. Elaboration of guides may include simply adding a clamp to existing simple guide bars, or creating a special purpose jig which both clamps the Held Tool in place, and rolls along the cutting wheel or disk. In one such common jig, for instance, two halves of the jig are positioned along a slide mechanism which allows the two halves to move toward or away from one another. The two halves of such common jig are formed with edges which may close on a Held Tool, and thereby clamp it in position in the common jig, as the halves of the common jig close toward one another. Such a common jig is generally provided with a screw closure mechanism, by which the user may move the halves of the jig together by turning such closure mechanism, thereby clamping a Held Tool within the jig. Such a jig is generally also provided with a wheel, by which the jig, with Held Tool clamped in position, may be rolled against the grinding wheel or disk, to thereby maintain the Held Tool at the proper distance and angular orientation from the grinder.
However, existing guide bars and jigs are not set up for, or adaptable to, accurately maintaining the proper relationship between the grinding surface and the Held Tool. For instance, with a simple guide bar, merely resting the Held Tool against the bar, while moving the end of the Held Tool so that its edge is near or against the grinding surface, does not insure the edge of the Held Tool always bears against the grinding surface at the same angle. And common sharpening jigs do not improve accuracy in angular placement, but may even exacerbate this problem as the wheel upon which the jig depends for proper distance above the grinding surface allows the user to rotate the Held Tool around the axis of the wheel. Such rotation allows easy movement in angular position of the common jig, and the Held Tool in relation to the grinding surface with the common jig.
Moreover, jigs of common design depend for their operation on a narrow wheel. Such a narrow wheel can set the distance of the jig as a whole from the grinding surface, but still allow the common jig to rock from side to side, laterally. Such lateral movement of the common jig allows the Held Tool to rotate along its axis as it bears against the grinding surface, thereby grinding one side of the Held Tool more than the other side. Such insecure positioning of the Held Tool is precisely the opposite of the desirable firm positioning necessary to an accurate grinding.
Finally, jigs which have positioning wheels, even as they provide guidance for the Held Tool near its point of attachment to the jig, cannot provide guidance of the Held Tool close to its end, near the edge to be sharpened, because the wheel of such a jig must be kept substantially between the jig and the grinding surface. Truly accurate sharpening requires rigid control of the entire Held Tool. Such rigid control in turn requires the Held Tool be held rigidly, at two places along its length, or at least rigidly held at the distal end of the Held Tool, where the sharpening takes place. Any other arrangement is unlikely to be better than a simple guide bar, as the Held Tool in a common wheeled jig may rotate fully as much as (if not more than) the same Held Tool resting on a simple guide bar.
No apparatus or method for sharpening a Held Tool in the related art addresses the shortcomings encountered when working with guide bars and presently existing common sharpening jigs. In attempting to achieve accurate and reproducible sharpening results, and a sharpening regime in which the user sharpens less often and waists less of ones tool and time, others have created various sharpening apparatus, and sharpening guides to be used therewith or separately. Such apparatus and methods within the related art include:
U.S. Pat. No. 3,482,325 to Mitchell, which discloses a gauge for positioning drill bits for dressing on a grinding wheel.
U.S. Pat. No. 4,270,315 to Reiling et al., which discloses a fixture for holding a twist drill to be regound.
U.S. Pat. No. 5,295,328 to Olbrich, which discloses an apparatus for sharpening, grinding and polishing of dental, periodontal and/or surgical instruments.
U.S. Pat. No. 5,545,081 to Haffely et al., which discloses an apparatus for holding a tool having a cutting edge in a predetermined abrading orientation with respect to a tool abrading apparatus.
U.S. Pat. No. 5,944,592 to Hall et al., which discloses a sharpener apparatus comprising a linear bearing assembly mounted on a base, and a support block carried by the bearing assembly for reciprocating movement along a rectilinear path relative to the base.
U.S. Pat. No. 6,254,455 B1 to Irvine et al., which discloses a jig for use in sharpening a cutting implement for use in wood turning.
U.S. Pat. No. 6,447,384 B1 to Jansson, which discloses jig for grinding sharp-edged tools.
U.S. Pat. No. 6,676,495 B1 to Siemers et al., which discloses a powered sharpening system, and a tool rest used in conjunction therewith.
The inventions disclosed in these patents appear to fulfill their respective objectives. However, these prior patents do not describe or suggest an apparatus or method for sharpening a Held Tool in which a guide or jig accurately maintains the angular relationship between the grinding surface and the Held Tool, such that the correct bevel angle is created when sharpening the Held Tool. Such correct bevel must be that bevel appropriate for the cutting task at hand, and the same bevel sharpening after sharpening. No patent or jig of which the inventor is aware describes or suggests a jig which uses a roller to maintain an accurate distance between a Held Tool and a grinding surface, rather than a wheel. Such a roller prevents lateral, side to side, movement of the jig, thereby preventing a rolling of the Held Tool along its axis, with consequent uneven grinding of the Held Tool side to side. No patent or jig of which the inventor is aware provides support for the main body of the jig, and the main body of the Held Tool within the jig, and at the same time provides support for the Held Tool near its distal end, thereby insuring the Held Tool does not rotate in relation to the grinding surface, thereby changing the angle of the bevel at the edge of the Held Tool. Finally, no invention or jig of which the inventor is aware accomplishes all these functions in a simple, easy to use jig, in which the user may easily set the desired angle of the bevel to be created or maintained on a Held Tool consistently one sharpening to the next.
The present invention overcomes the drawbacks of prior inventions. A jig, with roller, is used for its small size, and ease of use with all kinds of sharpening systems, including both vertical sharpening wheels and horizontal sharpening disks or stones. The roller of the jig is formed to be wide enough to contact a large section of the cutting surface, thereby providing lateral stability so that the jig and Held Tool do not roll along the axis of the Held Tool. As a result, an accurately flat bevel is ground, with square profile, as the Held Tool does not roll out of square alignment with the cutting surface. The jig of the present invention has a clamp for holding the end of the Held Tool near its distal end during sharpening. As the clamp resides on one end of the Jig, which end is nearest the grinding surface during sharpening, the angle at which the tool is held against the grinding surface is kept constant, as the distal end of the Held Too is held securely in place, thereby preventing grinding imperfections due to flexure or vibration in the distal end of the Held Tool.